In the past in the case of a broad pay zone or multi pay zone to be completed the procedure was to break it into sections. The fracturing and gravel packing equipment is run into cased and perforated hole along with an isolation packer. The packer would be set to isolate the lowermost zone and the isolated zone would then be fractured below that packer. Thereafter, gravel would be delivered outside screens through a crossover to fill the annular space around the screen with gravel. After that the packer would remain in the zone just gravel packed along with the screens with gravel on their exterior as the crossover and associated wash pipe were pulled out through the already set packer. After that zone was isolated, fractured, and gravel packed another trip in the hole with a similar assembly as used for the lowest zone would be run in for doing the same for the next zone up. This process continued until all zones or sections of a continuous zone were completed.
This technique required many trips in and out of the wellbore and that translated into very high expenses for rig time. One of the reasons that this staged procedure was used was that to do it another way where an entire interval could be isolated and fractured and gravel packed at once required packers to then be set in the annulus after gravel packing. The packers that had been available were not known for reliable sealing against the inside wall of casing if the annular space was full of gravel.
More recently packer designs have evolved and sealing in an annulus that is full of gravel is possible. An example of such a packer is U.S. Pat. No. 6,896,049. Other packer designs are illustrated in U.S. Pat. Nos. 6,782,946; 5,988,276; 6,009,951; 7,100,690; 5,184,677 and 6,513,600.
Packers that push gravel out of the way for a metal to metal seal in cased hole have been suggested in a multi-zone completion method described in US Publication 2008/0164026. The issue with the metal to metal seal packers is the high force required to push the gravel aside while a complex crossover is still in the hole.
The present invention seeks to build on the technique of multiple zone fracturing and gravel packing by creating a barrier between producing zones that are gravel packed together by injecting fluid into the gravel packed annulus that forms a barrier between or among the zones. The injected material is a sealing material that is known in the art and some examples are discussed in U.S. Pat. Nos. 5,942,031 and 4,797,159. In the preferred embodiment the material is placed in the same trip as the gravel packing and the wash pipe with a shifting tool integrated into it is used to inject the chemical into the desired locations between zones to create barriers. The chemical can be stored inside the outer assembly and the shifter associated with the wash pipe can sequentially evacuate the chambers with the chemical into the annular space to create a barrier or barriers as required. These and other features of the present invention will be more readily apparent to those skilled in the art from a review of the detailed description of the preferred embodiment and the associated drawings with the understanding that the full scope of the invention is determined by the appended claims.